Reduction gearing



7 July 1927.,

1,634,863 R. C. 'ALLEN REDUCTION" GEARING Filed May 10. 1921 I VENTOR cal. gearing is customarily usedowing to the.-

Patented 'July 5, 1 927.

UNITED STATES res st-a ATE-r OFFIQE.

ROBERT C. ALLEN,

REDUCTION enARrNe.

Application filed May 10, 1921 Serial No. 463,294.

My invention relates to a method of grind-- ing gears and has for its object to provide a method in which the toothsurfaces shall be uniformly ground throughout, thereby resulting in accurate tooth shapes and smooth surfaces.

Apparatus whereby my method may be carried out is illustrated in theaccompanying drawings, forming a part of this application, in which, I e

Figure 1 is a diagrammatic detail view of a pair of meshing gear elements;. and v Figure '2 is a side elevation of a gear grinding rig. In-:. reduction gearing for reducing ,the speed of high power apparatus, for example, steam turbines, it is necessary to use gearing possessing sufficient strength and, at the same time, it should not be unnecessarily cumbersome. For these reasons, double helifeature of overlapping engagement of the teeth. However, with gearing of this type,

it is necessary that the tooth surfaces shall.

be made as accurately as possible to minimize vibration and therefore to increase the efficiency and durability of the installation.

In order to produceaccurate tooth-.sur-' it is usual, after a gear-has been cut faces, on a hobbing machine, to a finishing or grinding operation. dinarily, this is carried outby mounting the gear in ,an appropriate rig and driving the gear by means of a pinion inthe presence of an abrasive. subject to the difiiculty that-the pinion has only a rolling action with the gear at the pitch circle 'ofthe gear and sliding action with. respectto the gear teeth in the dedendum and addendum portions thereof. It will be obvious therefore that grinding takes place where sliding occurs and that no grinding action takes place in the Vicinity of the pitch circle. Consequently, any metal that is removed at the pitch circle is rolled to submit the teeth or forged out rather than out by the abra-Q improved method, I am able to produce clearly indicate the method involved. .Figure 2, a grinding rig 1s shown having This process, however, is

but also at the pitch circle. .By my gears having more accurate tooth shapes and smoothersurfaces. than heretofore possible.

' Referring now to thedrawingsfor a more detailed description-of my invention, 1. will consider Figure 2 first in order to more In OF ESSINGTON', PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE a main frame 10 for' supporting the gear to be ground. A supplemental frame 11 for the pinion is adjustable with respect to'the main frame in order to secure proper meshing of the pinion and the gear. The pinion-is adapted to be driven by any suitable source of power 1.2 acting through a belt 13.

The main frame l0-is provided'with suitable supporting rollers 14 for the journal portions 15 of'the gear 16. The supplemental frame 11 is provided with supporting rollers 20 and adjustable rollers 17 for the journal portions 18 of the pinion 19. The supplemental frame is slidably mounted on the main frame 10 of-the rig and'is pro-. vide'd-with laterally projecting lugs 21, one of which is shown in Figure 2. The main frame lO-is provided'with lugs 22, in line with portions of the lugs 21 and which carry threaded bolt members 23 adapted to 00- I supplemental frame. .It 'will be obvious therefore that, by adjusting the screws 23,

the supplemental frame member may be accurately adjusted with reference to the main frame member 10 of the rig in order to. properlymesh'the teeth of the pinion and the gear.

It isnecessary to provide top rollers 17 n connection with the journal portions 18 of the pinion member in order to maintain the pinion member in place. The rollers 17 are adjustable in order to accommodate pinion journal portions of varying diameters, and, for this purpose, the rollers 17 are carried by appropriate bifurcated members orharps 24 fitting within appropriate guide-ways 25 of the'overhanging end 26 of the su lemental frame member 11. Screws 27 cooperate with I the bifurcated members or harps inorder to secure proper adjustments of the rollers 17. A suitable brake 28 is'associated with the gear 16 in order to resist rotation or to load the latter when the gear is driven by means operate with the projecting lugs 21 of the of the pinion, the latter in turn being driven by the source of power.

In normal operation, the pinion 19 drives the gear 16 against the load imposed by the able for carrying out my proccss,1 will now disclose mynovel method of grinding. Figure 1 shows enlarged fragments of the mesh ing gear 16 and pinion 19. In this View,

it the pinion 19 is of the proper size or has teeth of the proper shapes, the pitch line thereof has, with reference to the standard teeth of the gear 16,- a definite location indicated at A. i i

If a second )llllOIl, with the same diameter blank, is-cut, ut with one more tooth than the first pinion, it. can be provedthat the pitch line, or locus of points where rolling occurs, will move inward alongthe normal dedendum portion of the gear to some point indicated by the line C.

If a third pinion, with the same diameter of blank as the first pinion, is cut, but with one less tooth than the first pinion, it can he proved that the pitch line will move outward along the addendum portion of the gear teeth to positions indicated by the line B.

If three; pinions' are made .as indicated above and the same gear 16 is ground, first with the second pinion having onemore tooth than standard, using an abrasive of the character indicated, then followed with the third pinion having one less tooth than standard, and finished with the standard size blank, all portions of the gear teeth will be actually cut by the abrasive at one of the operations, resulting in a smooth, true surface approximating the desired involute curve.-

It will be obvious that a single pinion may be used and the supplemental frame member adjusted in order to allow the pinion to be accurately adjusted to various depths of engagement.

It will also be obvious to those skilled in the art that the grinding pinions used need not have varying numbers of teeth, but may have a constant number of teeth and the above described result obtained by making one blank standard, one slightly over size, and the third under size.

From the above, itwill be seen that I have devised a method for grinding gearsin which the entire tooth surface is ground, thereby obtaining accurate tooth shapes and smooth surfaces. I

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is sus- Ceptible of various other changes and modi- 2. A process of grinding gears which consists in resisting the freedom of a gear to rotate. driving the gear by two pinions having pitch circle relationships with the gear below and above the normal pitch circle thereof respectively supplying an abrasive to the contracting portions, and driving the gear by means of a standard pinion having pitch circle relationship with the gear at the standard pitch circle thereof in the presence of an abrasive, the distance between the centers of the gear and each pinion being constant.

3. A process of grinding gears which consists in resisting the freedom of a gear to rotate, and successively driving said gear in the presence of an abrasive by a plurality ot pinions, each pinion having more or less teeth than its predecessor and the distance 'between the centers of the gear and the various pinions in mesh therewith being constant.

4. A process of grinding gears which consists in loading agear to be ground, and successively driving said gear with independent pinions having greater than normal, normal and subnormal pitch circles, respectively, in the. presence of an abrasive.

The method of grinding gears which consists in loading the gear to be ground, driving the geanby a plurality of pinions which act independently and successively to engage the teeth of the gear with a rolling action within, at, and without the pitch circle thereof respectively, and subjecting substantially the entire face and flank portions of the teeth thereof'to a sliding action.

In testimony whereof, I have hereunto subscribed my name this 28th day of April, 1921.

ROBERT C. ALLEN. 

